1. Field of the Invention
This invention relates to a method of chemically polishing copper and copper alloys. More particularly, it is concerned with a method of chemically polishing copper and copper alloys using a solution with organic compound(s) selected from azoles added to an aqueous solution containing hydrogen peroxide and sulfuric or nitric acid. An object of the invention is to provide a uniform brilliant surface by a safe and easy treatment.
2. Description of the Prior Art
Chemical polishing of copper and copper alloy materials is widely used in industrial fields for the production of decorations, electric parts, camera parts, lighter parts and the like. As the method of chemically polishing the surface of copper and copper alloy materials have heretofore been employed nitric, sulfuric and hydrochloric acid-containing mixed aqueous solutions. They are, however, disadvantageous in that production of materials with a definite quality is considerably delicate, toxic nitrous gas is evolved during the operation, etc.
As an improvement of these disadvantages there is known a method comprising the treatment with an aqueous solution containing hydrogen peroxide and sulfuric or nitric acid to form an oxidized coating upon the metal surface and subsequent removal of the oxidized coating by solubilization to afford a brilliant surface. This method involves formation of a coating of oxide upon the metal surface, which is secondarily dissolved in the polishing solution whereby repeated formation and dissolving of an oxidized coating results in smoothness of the surface. However, repetition of the formation of an oxidized coating and the dissolving of the oxidized coating into the polishing solution will be possible if the molar ratio of hydrogen peroxide to the acid is specified within a very small range. Beyond the range, there is obtained no polishing effect at all. It is therefore necessary to constantly maintain the hydrogen peroxide to acid molar ratio within a small range and furthermore there is needed procedures for removing the oxidized coating formed in the chemical polishing by dissolving in a separate bath with a result that more treatment steps are disadvantageously involved.